1. Field of the Invention
The present invention relates to a method for manufacturing a liquid discharge head which discharges liquids, and more particularly to a method for manufacturing an inkjet recording head.
2. Description of the Related Art
As an example of a liquid discharge head which discharges liquids, an inkjet recording system for discharging inks to a recording medium to perform recording can be cited.
An inkjet recording head applied to the inkjet recording system (liquid jet recording system) generally includes a plurality of minute discharge ports, liquid flow paths, and energy generating elements disposed in a part of the liquid flow paths to generate energy used for discharging liquids. As a conventional method for manufacturing such an inkjet recording head, for example, U.S. Pat. No. 6,390,606 discusses the following method.
First, an adhesive layer is formed on a substrate having energy generating elements formed thereon to improve adhesiveness between a flow path forming member, which is formed later, and the substrate. A soluble resin layer is applied to the adhesive layer and patterned to form a pattern of an ink flow path. Then, a cover resin layer, including an epoxy resin and a photo cationic polymerization initiator, is formed to be an ink flow path wall on the ink flow path pattern, and discharge ports are formed on the energy generating elements by photolithography. Lastly, the soluble resin is eluted and the cover resin layer which becomes a flow path forming member is cured.
However, in an inkjet recording head produced experimentally based on the method discussed in U.S. Pat. No. 6,390,606, the present inventors found that depending on diameters of discharge ports and types of inks, discharged droplets were random and did not land on desired impact positions.
It was observed that very small particulate substances were often sticking near the discharge ports. It is speculated that misted ink droplets called mist generated during ink discharging sticks to the particulate substances to accumulate, so that a direction of the discharged ink droplets was affected by ink puddles sticking to the discharge port surfaces and became random.
A close study of the phenomenon was made and it is considered that the following process causes sticking of particulate substances. That is, the flowpath forming member, the adhesive layer disposed between the member and the substrate, or adhesives were dissolved during manufacturing, and subsequently guided near the discharge ports. As a specific example, a solvent used for applying a member to form a flow path pattern on the adhesive layer causes molecules of the adhesive layer to be lowered, and the low molecule adhesive layer sticks as eluted substances to the discharge port surfaces when the flow path pattern is eluted. A level of sticking of the particulate substances to the discharge port surfaces varies depending on materials for the flow path forming member, the adhesive layer, and the flow path pattern, and the solvent. The materials for the flow path forming member, the adhesive layer, and the flow path pattern may be changed. However, such a change may narrow material options.
As observed in a recent inkjet recording head, very small ink droplets of several picoliters (pl) discharged from the minute discharge ports are easily affected by the ink droplets sticking to the discharge port surfaces as described above. Thus, it is desired that generation of substances sticking to the discharge port surfaces should be avoided as much as possible to limit an influence on the discharged ink droplets to a minimum.